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18
Delaybased network utility maximization
 in Proc. IEEE INFOCOM 2010
, 2010
"... Abstract—It is well known that maxweight policies based on a queue backlog index can be used to stabilize stochastic networks, and that similar stability results hold if a delay index is used. Using Lyapunov Optimization, we extend this analysis to design a utility maximizing algorithm that uses ex ..."
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Abstract—It is well known that maxweight policies based on a queue backlog index can be used to stabilize stochastic networks, and that similar stability results hold if a delay index is used. Using Lyapunov Optimization, we extend this analysis to design a utility maximizing algorithm that uses explicit delay information from the headofline packet at each user. The resulting policy is shown to ensure deterministic worstcase delay guarantees, and to yield a throughpututility that differs from the optimally fair value by an amount that is inversely proportional to the delay guarantee. Our results hold for a general class of 1hop networks, including packet switches and multiuser wireless systems with time varying reliability. I.
Throughput optimality of delaydriven MaxWeight scheduler for a wireless system with flow dynamics
"... Abstract—We consider a wireless downlink shared by a dynamic population of flows. The flows of random size (bits) arrive at the base station at random times, and leave when they have been completely transmitted. The transmission rate supported by the wireless channel of each flow while the flow awai ..."
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Cited by 10 (1 self)
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Abstract—We consider a wireless downlink shared by a dynamic population of flows. The flows of random size (bits) arrive at the base station at random times, and leave when they have been completely transmitted. The transmission rate supported by the wireless channel of each flow while the flow awaits transmission varies randomly over time and is independent of that of the other flows. The scheduling problem in this context is to select a flow for transmission based on the current system state (e.g., backlogs, wait times, and channel states of the contending flows). It has recently been shown that for such a system, the wellknown (backlogdriven) MaxWeight scheduler is not throughput optimal. That is to say, the MaxWeight scheduler will not stabilize a given system even though it is possible to construct a stabilizing scheduler using the various flow and channelrelated statistics. However, in this paper, we show that the delaydriven MaxWeight scheduler is, nevertheless, throughput optimal for such a system. The delaydriven MaxWeight, like its backlogdriven version, does not require any knowledge of the flow or channelrelated statistics. I.
Delay Efficient Scheduling via Redundant Constraints in Multihop Networks
, 2010
"... Abstract—We consider the problem of delayefficient scheduling in general multihop networks. While the class of maxweight type algorithms are known to be throughput optimal for this problem, they typically incur undesired delay performance. In this paper, we propose the DelayEfficient SCheduling a ..."
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Cited by 4 (1 self)
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Abstract—We consider the problem of delayefficient scheduling in general multihop networks. While the class of maxweight type algorithms are known to be throughput optimal for this problem, they typically incur undesired delay performance. In this paper, we propose the DelayEfficient SCheduling algorithm (DESC). DESC is built upon the idea of accelerating queues (AQ), which are virtual queues that quickly propagate the traffic arrival information along the routing paths. DESC is motivated by the use of redundant constraints to accelerate convergence in the classic optimization context. We show that DESC is throughputoptimal. The delay bound of DESC can be better than previous bounds of the maxweight type algorithms which did not use such traffic information. We also show that under DESC, the service rates allocated to the flows converge quickly to their target values and the average total “network service lag ” is small. In particular, when there are O(1) flows and the rate vector is of Θ(1) distance away from the boundary of the capacity region, the average total “service lag ” only grows linearly in the network size.
Large deviation sumqueue optimality of a radial sumrate monotone opportunistic scheduler
, 2009
"... ..."
Stability and asymptotic optimality of opportunistic schedulers in wireless systems
"... We investigate the scheduling of a common resource between several concurrent users when the feasible transmission rate of each user varies randomly over time. Time is slotted and users arrive and depart upon service completion. This may model for example the flowlevel behavior of endusers in a na ..."
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We investigate the scheduling of a common resource between several concurrent users when the feasible transmission rate of each user varies randomly over time. Time is slotted and users arrive and depart upon service completion. This may model for example the flowlevel behavior of endusers in a narrowband HDR wireless channel (CDMA 1xEVDO). As performance criteria we consider the stability of the system and the mean delay experienced by the users. Given the complexity of the problem we investigate the fluidscaled system, which allows to obtain important results and insights for the original system: (1) We characterize for a large class of scheduling policies the stability conditions and identify a set of maximum stable policies, giving in each time slot preference to users being in their best possible channel condition. We find in particular that many opportunistic scheduling policies like ScoreBased [9], Proportionally Best [1] or Potential Improvement [4] are stable under the maximum stability conditions, whereas RelativeBest [10] or the cµrule are not. (2) We show that choosing the right tiebreaking rule is crucial for the performance (e.g. average delay) as perceived by a user. We prove that a policy is asymptotically optimal if it is maximum stable and the tiebreaking rule gives priority to the user with the highest departure probability. In particular, we show that simple priorityindex policies with a myopic tiebreaking rule, are stable and asymptotically optimal. All our findings are validated with extensive numerical experiments.
Limiting Properties of Overloaded Multiuser Wireless Systems With ThroughputOptimal Scheduling
, 2014
"... Throughputoptimal scheduling has been widely discussed due to its capability to stabilize singlehop multiuser wireless systems if possible. However, most of the previous discussions focused on the underloaded scenario, i.e., the arrival rate lies inside the achievable rate region. The behavior of ..."
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Throughputoptimal scheduling has been widely discussed due to its capability to stabilize singlehop multiuser wireless systems if possible. However, most of the previous discussions focused on the underloaded scenario, i.e., the arrival rate lies inside the achievable rate region. The behavior of throughputoptimal scheduling in overloaded multiuser wireless systems is the focus of this paper. We first show that, with the infinite buffer assumption, although all the queues are unstable, both the average throughput and a function of queue length converge as time evolves. In addition, the average throughput is the solution to a convex optimization problem whose objective is determined by the scheduling algorithm. By investigating the average throughput of two special throughputoptimal scheduling algorithms, i.e., the generalized MaxWeight and LogRule, we find that users can be prioritized by tuning the parameters associated with the scheduling algorithm, but the fairness is not likely to be guaranteed and some users may starve. Second, by studying the finite buffer system, we show that whether the buffer is dedicated to each queue or shared among queues has a great impact on the system performance, and the potential user starvation problem can be alleviated by a proper design.
Joint Realtime and NonRealtime Flows, Packet Scheduling and Resource Block Allocation in Wireless OFDMA Networks
"... Abstract—In this paper, we consider joint realtime (RT) and nonrealtime (NRT) flows packet scheduling and resource block (RB) allocation in orthogonal frequency division multiple access (OFDMA) wireless networks. Radio resource blocks (RB)s in OFDMA plane are to be distributed among RT and NRT flow ..."
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Abstract—In this paper, we consider joint realtime (RT) and nonrealtime (NRT) flows packet scheduling and resource block (RB) allocation in orthogonal frequency division multiple access (OFDMA) wireless networks. Radio resource blocks (RB)s in OFDMA plane are to be distributed among RT and NRT flows. In the conventional approach, RT and NRT flows are served sequentially. This sequential approach is inefficient, because an RT flow may presumably have enough time until its delay deadline while its channel is in deep fade. In this situation, the transmission of NRT flows with higher level of efficiency can be performed. Intuitively speaking, the conventional sequential approach is too conservative that can be reengineered. We propose a novel joint RT and NRT flows disutilitybased packet scheduling and RB allocation, in a common pool of RBs. The proposed joint approach enlarges the effective capacity of the associated wireless system,
LaxityBased Opportunistic Scheduling with FlowLevel Dynamics and Deadlines
"... Abstract—Many data applications in the next generation cellular networks, such as content precaching and video progressive downloading, require flowlevel quality of service (QoS) guarantees. One such requirement is deadline, where the transmission task needs to be completed before the applications ..."
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Abstract—Many data applications in the next generation cellular networks, such as content precaching and video progressive downloading, require flowlevel quality of service (QoS) guarantees. One such requirement is deadline, where the transmission task needs to be completed before the applicationspecific time. To minimize the number of uncompleted transmission tasks, we study laxitybased scheduling policies in this paper. We propose a LessLaxityHigherPossibleRate (L 2 HPR) policy and prove its asymptotic optimality in underloaded identicaldeadline systems. The asymptotic optimality of L 2 HPR can be applied to estimate the schedulability of a system and provide insights on the design of scheduling policies for general systems. Based on it, we propose a framework and three heuristic policies for practical systems. Simulation results demonstrate the asymptotic optimality of L 2 HPR and performance improvement of proposed policies over greedy policies. I.
Study of Downlink Scheduling Algorithms in LTE Networks
"... Abstract—Long Term Evolution (LTE) is one of the fastest growing technologies which supports variety of applications like video conferencing, video streaming, VoIP, file transfer, web browsing etc. In order to support multiple applications, Radio Resource Management (RRM) procedure is one of the key ..."
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Abstract—Long Term Evolution (LTE) is one of the fastest growing technologies which supports variety of applications like video conferencing, video streaming, VoIP, file transfer, web browsing etc. In order to support multiple applications, Radio Resource Management (RRM) procedure is one of the key design roles for improving the system performance. LTE system effectively utilizes the resources by dynamically scheduling the users in both frequency and time domain. However, scheduling algorithms are not defined in the Third Generation Partnership Project (3GPP) specifications. Therefore, it becomes one of the special interests for service providers. In this paper a study of downlink scheduling algorithms present in the literature is put forth and performance evaluation of four algorithms proposed for LTE downlink is carried out. This paper also discusses the key issues of scheduling algorithms to be considered for future traffic requirements.